Subscribe button is not working

I installed the Feature box lite. Everything went fine until I actually tested whether the Subscribe button in my feature box works or not. It didn’t. I sent an email to their customer support and received a reply with a link to instructions. I had followed the instructions in the first place and replied that it’s just not working. I haven’t heard from them since and it’s been three days.

There are also some serious problems with editing the feature box. This plugin doesn’t seem reliable to me.